London has to provide housing for a million more people by 2016, taking into account new arrivals, plus old-timers who need an upgrade. Since space is limited, UK company Popularchitecture is proposing a 5,000-foot high tower that would house pretty much everybody all in one shot—and reduce four city neighborhoods to a single cylindrical building. See the whole thing below.

The tower, which at this point remains simply a novel idea, would take up little actual ground space and run like a proper democracy. It is literally broken up into municipal areas—the "neighborhood" is a singe floor of 600; the village is 20 floors and houses 6,000. There are also three super-districts that house 33,000 people each.

Elected reps serve in a local government and have regular meetings to decide what to do with common areas, which would include an ice skating rink, a botanical garden, an open-air theater, and tennis courts.
Circular openings in sections of the tower will provide nature-y parks and gardens for citizens. Five circulation cores with massive elevators—think the Tube, except it goes up and down instead of weaving underground—transport residents from neighborhood to neighborhood. Water and waste will be recycled, and fresh water harvested from the clouds, which pretty much start right around where the tower's peak ends.

Since your workplace, your local movie theater, and all your friends will be in the same building, you'll ever have to leave.